'I won't fight you.'
'Oh, but you will.' The voice twisted and cracked. Fury and madness tore through it. 'You will fight me, Doctor!'
The Doctor is on the run from a faceless enemy that knows his every thought and move. He flees to his past, planning to leave Ace in safe hands in order to fight on alone. But his enemy has other plans, and the Doctor's history no longer exists.
The TARDIS is finally drawn to London in the winter of 1888, where the Doctor and Ace discover a dark secret from Gallifrey's past, and the name of their unseen opponent.
It is Jack the Ripper.